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BQ25302: Switching from CC charging to CV charging

Y.Ottey
Mastermind 6145 points
Part Number: BQ25302
Other Parts Discussed in Thread: BQ25606, , BQ25618

Dear TI Team

We are currently comparing charging times under the following conditions.
A: Using BQ25606, set the maximum charging current ICHG = 2.4A
B: Using BQ25302, set the maximum charging current ICHG = 2A

When it was carried out, B had a shorter charging time.
I wondered that the maximum charging current was shorter in B but shorter than in A.
I got the charging current and voltage data as follows.

Then, BQ25302 switched from CC charging to CV charging later than BQ25606.
We believe that this has shortened the charging time of the BQ25302.
Is the difference in switching time between CC charging and CV charging due to the device?
(Of course, the difference in charging time may be due to the difference in charging termination current.)

Best Regards,
Y.Ottey

  • 0
    TI__Mastermind 24075 points

    Hi,

       The termination is one factor, and the other is that the BAT pin on BQ25302 is not a power pin, but a sense pin. It senses the battery voltage and can be tied closer to the battery itself allowing for more accurate battery voltage sensing. This allows for more time in the CC charging phase. Similar to the BQ25606 are the BQ25618/619 which have all the features of BQ25606 but also provides a BATSNS pin.

  • 0 in reply to Kedar Manishankar
    Mastermind 6145 points

    Hi Manishankar,

    Thank you for your reply.

    I understand the difference between BQ25302 and BQ25606.
    I would like to ask you an additional question, but when I measured it with BQ25606 with a charging current of 2A, almost the same graph as in the case of BQ25302 was measured.
    (The only difference in charging time is the difference in charging termination current value.)

    I think that the detection accuracy of the charging voltage of BQ25606 has improved because the charging current has become smaller, but I am wondering if the charging current of 2.4A and the charging current of 2A are so different.
    I would be grateful if you could let me know if there are any other factors.
    (By the way, both are measured by EVM.)

    Regards,
    Y.Ottey

  • 0 in reply to Y.Ottey
    TI__Mastermind 24075 points

    Hi,

       If there is more impedance in the path, than the CV phase would take longer to charge which is what you observe. This would be more of layout and system consideration. Higher charge current across impedance results in a larger voltage drop. This is the purpose of the CV loop, to taper current to ensure battery is actually fully charged instead of just charging to Vreal_BAT + Iimp*Charge current. It is not just the EVM layout and setup, but also how the battery is connected. For example, if there are long wires between battery and EVM, protector/gauge in the path etc.